This invention relates to methods and apparatus for coupling rotating shafts together and to methods of fabricating coupling elements to connect rotating shafts one to the other.
In one class of coupling techniques for rotating shafts, at least one integrally formed coupling element is coupled by one group of circumferentially spaced fasteners to a first shaft and by a second group of circumferentially spaced fasteners to a second shaft. In this class of coupling elements, there are no moving parts except for flexing of the coupling element during rotation.
During rotation of this class of coupling element, the fasteners of the driving shaft apply force to the fasteners of the driven shaft through the coupling element so that the driver applies force to the coupling element which in turn applies force to the fasteners of the driven shaft and thus the driven shaft. The coupling element includes an even number of holes and the holes may include bushings to receive fasteners for the driver and the load so that a fastener to the driver pulls a fastener adjacent to it for the load through the coupling element.
In a prior art type of coupling technique of this class of coupling techniques, the coupling elements are metallic discs that are sufficiently thin to bend or flex and thus accommodate misalignment of the driver and load without intentional relative motion between the metal discs and without rolling or sliding parts. This prior art type of coupling in some embodiments uses a series or stock of thin metal discs. Because the discs are thin, they are capable of flexing and because a number of them are stacked, they may accommodate heavier loads.
This prior art type of coupling technique has several disadvantages such as: (1) if a single thick metal disc is utilized, it is not sufficiently flexible and does not permit a high degree of misalignment without imparting forces to the shaft and bearings of the driven shaft that cause excessive wear; (2) if a number of thin discs are utilized to permit greater flexibility, then there is some movement between the discs and the motion causes wear; (3) the coupling is subject to corrosion; and (4) such couplings are typically limited to approximately 1/4 degree misalignment for normal fatigue life and 1/2 degree for almost immediate failure.
Other types of prior art coupling techniques use elastomeric coupling elements, or elements formed of elastomeric material with wire or cord embeded in it. Such couplings have a disadvantage of not being able to handle large loads without excessive heating or fracturing in tension.